OGLE16aaa - a Signature of a Hungry Super Massive Black Hole

TL;DR

This paper reports the discovery of OGLE16aaa, an unusual transient event likely caused by a tidal disruption event (TDE) in a weakly active galaxy, suggesting a new subclass of TDEs associated with weak or recently active supermassive black holes.

Contribution

It introduces a new subclass of TDEs linked to weakly active SMBHs, challenging previous assumptions that TDEs only occur in inactive galaxies.

Findings

OGLE16aaa exhibits properties similar to other TDEs but in a weak-line AGN.

This class may bridge TDEs in quiescent and active galaxies.

Implications for TDE rate estimations and galaxy activity classifications.

Abstract

We present the discovery and first three months of follow-up observations of a currently on-going unusual transient detected by the OGLE-IV survey, located in the centre of a galaxy at redshift z=0.1655. The long rise to absolute magnitude of -20.5 mag, slow decline, very broad He and H spectral features make OGLE16aaa similar to other optical/UV Tidal Disruption Events (TDEs). Weak narrow emission lines in the spectrum and archival photometric observations suggest the host galaxy is a weak-line Active Galactic Nucleus (AGN), which has been accreting at higher rate in the past. OGLE16aaa, along with SDSS J0748, seems to form a sub-class of TDEs by weakly or recently active super-massive black holes (SMBHs). This class might bridge the TDEs by quiescent SMBHs and flares observed as "changing-look QSOs", if we interpret the latter as TDEs. If this picture is true, the previously applied requirement for identifying a flare as a TDE that it had to come from an inactive nucleus, could be leading to observational bias in TDE selection, thus affecting TDE-rate estimations.